Sheet № 131 · Foundation + Higher · AQA · Edexcel · OCR
Multiplying and Dividing Decimals –
Multiplying and dividing decimals without a calculator is a key non-calculator skill tested on Foundation and Higher GCSE Maths papers. The technique relies on ignoring the decimal point, performing the calculation with whole numbers, and then repositioning the point.
§Key definitions
Question:
Calculate 0.3 × 0.7.
Q1 (Foundation):
Calculate 0.4 × 0.8.
Q2 (Foundation):
Calculate 6.3 ÷ 0.9.
Q3 (Higher):
Calculate 0.045 × 200.
§Formulas to memorise
When multiplying decimals, count the total decimal places in both numbers — the answer has that many decimal places
When dividing by a decimal, multiply both numbers by 10, 100, etc. to make the divisor a whole number
Worked example
Calculate 0.3 × 0.7.
Working:
⚠ Common mistakes
- ✗Placing the decimal point incorrectly after multiplying. Always count the total decimal places from the original numbers, not from the product of the whole numbers.
- ✗Forgetting to adjust both numbers when dividing. When you multiply the divisor by 10, you must also multiply the dividend by 10 to keep the calculation equivalent.
- ✗Dropping trailing zeros. When counting decimal places, include any trailing zeros — 2.50 counts as 2 decimal places.
✦ Exam tips
- →For multiplying, use partitioning or the grid method if long multiplication feels tricky.
- →Always do a rough estimate first (e.g. 3.42 × 2.5 ≈ 3 × 3 = 9) to check your answer is reasonable.
- →On division questions, convert to a whole-number divisor immediately — it makes the working far simpler.